October 27, 2011
09:00 AM (EDT)

News Release Number: STScI-2011-30

Astronomers Pin Down Galaxy Collision Rate

October 27, 2011: A new analysis of Hubble surveys, including the All-Wavelength Extended
Groth Strip International Survey (AEGIS), the Cosmological Evolution
Survey (COSMOS), and the Great Observatories Origins Deep Survey
(GOODS), combined with simulations of galaxy interactions, reveals that
the merger rate of galaxies over the last 8 billion to 9 billion years
falls between previous estimates.

The galaxy merger rate is one of the fundamental measures of galaxy
evolution, yielding clues to how galaxies bulked up over time through
encounters with other galaxies. And yet, a huge discrepancy exists over
how often galaxies coalesced in the past. Earlier measurements of galaxies in
deep-field surveys made by NASA's Hubble Space Telescope generated a
broad range of results: anywhere from 5 percent to 25 percent of the
galaxies were merging. Results from this new study are accepted for publication in The Astrophysical Journal.